无槽丝锥通常用来加工螺距不大于2～2.5毫米的内螺纹,加工更大螺距的螺纹则不适用,因为切削力和表面粗糙度都会急剧增大。将无槽丝锥只用于普通丝锥粗切后精加工螺纹的尝试,也未收到好效果,因为在螺纹内径上会形成超出公差范围的毛刺。为了减小切削力和提高螺纹质量,设计了一种复合丝锥(图1),这种丝锥除具有挤压凸台1外,在每个刃瓣上还有切削齿2。在切削锥部分上,沿挤压凸台作有全牙形锥螺纹,而在校准部分上,作有圆柱螺纹。丝锥切削齿 Slotless taps are commonly used to machine internal threads with a pitch of no more than 2 to 2.5 mm and threads of larger pitch are not suitable because of sharp increases in cutting forces and surface roughness. Attempts to use a slotless tap only for roughing of a normal tap have not received any good results because of the formation of burrs outside the tolerance range on the inside diameter of the thread. In order to reduce the cutting force and improve the quality of the thread, a composite tap (Fig. 1) is designed which, in addition to the extrusion bosses 1, also has cutting teeth 2 on each blade. In the cutting cone portion, along the extrusion bosses made full conical thread, and in the calibration part, as a cylindrical thread. Taps cut teeth